Climate Change — Drills · Grade 12 Science

Chapter: Pollution, Carbon & Climate Evidence

What these drills covers

By the end of Climate Change you should be able to:

6 questions, multiple choice, numeric and written answer, each with a worked explanation.

Vocabulary used: greenhouse effect, greenhouse gas, fossil fuel, carbon cycle, climate feedback.

Problem 1

What does the greenhouse effect do?
  1. Traps some of Earth's outgoing heat, keeping the surface warmer
  2. Blocks all sunlight from reaching Earth's surface
  3. Removes carbon dioxide from the atmosphere
  4. Cools the planet by reflecting heat straight back to space
Answer and explanation

Traps some of Earth's outgoing heat, keeping the surface warmer

Greenhouse gases absorb outgoing infrared heat and re-emit some of it back down, keeping Earth's surface far warmer than it would otherwise be.

Problem 2

Which of these is NOT a significant greenhouse gas?
  1. Methane
  2. Nitrogen (N2)
  3. Water vapor
  4. Carbon dioxide
Answer and explanation

Nitrogen (N2)

Nitrogen makes up most of the atmosphere but does not absorb outgoing heat the way carbon dioxide, methane, and water vapor do.

Problem 3

Using the supplied comparison 280ppm to 420ppm, The Keeling Curve shows atmospheric CO2 rising from about 315 ppm in 1958 to about 420 ppm in this supplied model. What is the increase, in ppm?
Answer and explanation

105 ppm

420 - 315 = 105 ppm of carbon dioxide added since continuous measurements began in 1958.

Problem 4

Name two independent lines of evidence that Earth's climate is warming.
Answer and explanation

Any two of: the rising global surface-temperature record; shrinking glaciers and polar ice sheets; declining Arctic sea ice; rising sea level; warming ocean waters; and earlier spring events such as blooming and migration. These separate measurements all point to the same warming trend.

Problem 5

Which of these is an example of a positive climate feedback that amplifies warming?
  1. Clouds reflecting some sunlight back to space
  2. Plants absorbing carbon dioxide during photosynthesis
  3. Melting ice exposing dark water that absorbs more heat, melting still more ice
  4. The deep ocean storing heat for centuries
Answer and explanation

Melting ice exposing dark water that absorbs more heat, melting still more ice

The ice-albedo feedback is self-reinforcing: warming melts reflective ice, exposing dark water that absorbs more heat and melts even more ice.

Problem 6

Explain why scientists are confident that recent warming is caused by human-added greenhouse gases rather than by changes in the Sun.
Answer and explanation

The extra carbon dioxide carries an isotopic 'fingerprint' matching fossil fuels, so we can trace it to human burning. The Sun's measured output has not increased enough to explain the warming, and if a brighter Sun were the cause, the whole atmosphere would warm — but instead the upper atmosphere is cooling while the surface warms, which is the signature of heat being trapped near the surface by greenhouse gases.

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